Constrained minimum intensity projection for improved visualization of susceptibility weighted images

Authors

• MA Castro
• DL Pham
• JA Butman

Abstract

Minimum intensity projection (minIP) is a technique commonly used in susceptibility weighted imaging (SWI) to display the minimum intensity within a thick slab, allowing the observer to better visualize microhemorrhages and vessels in the brain. Unfortunately, the skull within the thick slab also exhibits low intensities in SWI and can mask superficial tissues. This can limit the ability to detect cortical microhemorrhages, which are a common feature of traumatic brain injury. As an alternative, we propose the idea of a constrained minIP that excludes skull and extracranial tissues from the minIP computation. We developed a methodology to automatically determine the brain mask for SWI. It first finds the optimal edge detection parameter of a brain surface extraction algorithm using a template-based approach. Morphological operations are then applied to guarantee a connected mask with smooth boundaries. Finally, the mean intensity within the mask is assigned to all voxels outside the mask, preventing bone from dominating superficial regions in the projection, enabling superior visualization of cortical hemorrhages and vessels. To evaluate the method, we examined 22 SWI magnitude images that were arbitrarily selected from an IRB approved study of traumatic brain injury. All cases were examined for superficial brain microhemorrhages, and five subjects were identified as possessing cortical microhemorrhages using our constrained minIP methodology that were not visible using a conventional minIP.

Scientific Focus Area: Research Support Services

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